#! /bin/bash

val=`expr 2 + 2`
echo "2+2=$val";

a=10
b=20

val=`expr $a + $b`
echo "$a+$b=$val";

if [ $a == $b ]
then
  echo "a等于b";
else
  echo "a不等于b";
fi

if [ $a -lt $b ]
then
  echo "a小于b";
else
  echo "a大于b";
fi
